Field of the Invention
The present invention relates to a system and a method for lens shading compensation.
Descriptions of the Related Art
Image capture and processing functions are widely implemented in consumer electronic devices, such as digital camera, smart phone or tablet. Images are generally captured by an input module comprising image sensors and lens. The raw images thus captured are performed with various processing before being provided for display and/or storage. Some processing may be general for all types of image capture operations, including photo shooting or video recording, for example de-noise that removes defect pixels. Some may be specific for desired functions/effects. For example, high dynamic range (HDR) is performed to produce images covering wider brightness range by combining two or more images captured by different exposure settings. While some other processing may aim to fix issues due to hardware limitations. Lens shading effect is a common problem caused by the inhibit limitation of camera lens. Due to the curve shape and limited angle of the lens surface, the intensity of incident light coming from the edges and corners and received by image sensors would be weaker than that in the middle of the lens and thus causes distortion on the color channels. This is called as lens shading effect. The impact of lens shading also varies for different color channels. For example, red color channel is affected more severely than blue and green color channels. To solve this problem, lens shading compensation is performed to restore the color values at the edges and corners.